Light emitting diode and lens for the same

ABSTRACT

A lens for a light emitting diode is formed with a material having a refractive index of n, and the lens includes a base, a first curved circumferential surface extending from the base, a curved center-edge surface extending from the first curved circumferential surface, and a curved centermost surface extending from the curved center-edge surface. The base includes a groove for receiving a light emitting chip therein. In the lens, a distance from a center of the base to a point of the curved center-edge surface is always shorter than the radius of curvature for the point of the curved center-edge surface. The curved centermost surface has a concave shape with respect to the base. In addition, when an obtuse angle formed between a main axis of the lens and a tangent line of a point of the curved centermost surface is A 1,  and an acute angle formed between a straight line linking the center of the base to the point of the curved centermost surface and the main axis of the lens is A 2,  the lens satisfies the equation: A 1 +A 2 &lt;90+sin −1 (1/n).

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation Application of U.S. patentapplication Ser. No. 12/507,308 filed on Jul. 22, 2009 now U.S. Pat. No.7,963,680, which is a Divisional Application of U.S. patent applicationSer. No. 11/120,666 filed on May 3, 2005 now U.S. Pat. No. 7,572,036,which claims priority to Korean Patent Application No. 10-2004-0083146,filed on Oct. 18, 2004, the disclosures of which are incorporated byreference herein in their entireties.

BACKGROUND OF THE INVENTION

(a) Technical Field

The present disclosure relates to a light source for a display device.

(b) Discussion of the Related Art

Display devices used for image display such as in a television receiveror computer monitor are classified into a self-luminescence display anda light-receiving display requiring a separate light source. Lightemitting diode (LED), electroluminescence (EL), vacuum fluorescentdisplay (VFD), field emission display (FED), and plasma display panel(PDP) devices, etc., are included in the self-luminescence displaydevice, while liquid crystal displays (LCDs), etc., are included in thelight-receiving display devices.

The LCD includes, for example, a pair of panels individually havingelectrodes on their inner surfaces, and a dielectric anisotropy liquidcrystal layer interposed between the panels. In the LCD, a variation ofthe voltage difference between the field generating electrodes, i.e.,the variation in the strength of an electric field generated by theelectrodes, changes the transmittance of the light passing through theLCD, and thus desired images are obtained by controlling the voltagedifference between the electrodes.

In the LCD, a light may be a natural light or an artificial lightemitted from a light source unit separately employed in the LCD.

A backlight device is a representative artificial light source devicefor the LCD. The backlight device utilizes light emitting diodes (LEDs)or fluorescent lamps such as cold cathode fluorescent lamps (CCFLs),external electrode fluorescent lamps (EEFLs), etc., as the light source.

The LED is eco-friendly since it does not use mercury (Hg) and it hasstable characteristics. For these reasons, the LED is a preferred lightsource.

However, some problems may arise when the LED is used as a surface lightsource device. This is because the light rays emitted from the LED tendto condense to a narrow region.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, there is provided alens comprising: a base; a first curved circumferential surface upwardlyextending from the base; and a first curved central surface extendingfrom the first curved circumferential surface, wherein a distance fromthe center of the base to a point of the first curved central surface isshorter than the radius of curvature for the corresponding point of thefirst curved central surface.

The lens further comprises a central hollow portion upwardly formed fromthe base. The central hollow portion is comprised of a second curvedcircumferential surface and a second curved central surface extendingfrom the second curved circumferential surface, which are inner surfacesof the lens. In this lens, it is preferable that a distance from thecenter of the base to a point of the second curved central surface islonger than the radius of curvature for the corresponding point of thesecond curved central surface.

A boundary region of the second curved central surface and the secondcurved circumferential surface is preferably placed within about 20degrees to about 50 degrees with respect to the center of the base.Also, a boundary region of the first curved central surface and thefirst curved circumferential surface is placed within 20 degrees to 50degrees with respect to the center of the base.

In this lens, the base includes a groove for receiving a light emittingchip therein, and a distance from the center of the base to a point ofthe first curved circumferential surface is shorter than the radius ofcurvature for the corresponding point of the first curvedcircumferential surface.

According to another embodiment of the present invention, there isprovided a lens which is formed with a material having a refractiveindex of n, and which comprises: a base; a first curved circumferentialsurface upwardly extending from the base; a curved center-edge surfaceextending from the first curved circumferential surface; and a curvedcentermost surface extending from the curved center-edge surface.

Here, it is preferable that a distance from a center of the base to apoint of the curved center-edge surface is always shorter than theradius of curvature for the corresponding point of the curvedcenter-edge surface.

The curved centermost surface has a concave shape with respect to thebase.

Here, it is preferable that the lens is constructed to satisfy thefollowing equation:A1+A2<90+sin⁻¹(1/n),

wherein A1 is an obtuse angle formed between a main axis of the lens anda tangent line of a point of the curved centermost surface, and A2 is anacute angle formed between a straight line linking the center of thebase to the corresponding point of the curved centermost surface and themain axis of the lens.

The lens further comprises a central hollow portion upwardly formed fromthe base of the lens. The central hollow portion includes a secondcurved circumferential surface and a curved central surface extendingfrom the second curved circumferential surface, which are inner surfacesof the lens.

Here, it is preferable that a distance from the center of the base to apoint of the curved central surface is longer than the radius ofcurvature for the corresponding point of the curved central surface.When the main axis of the lens is intersected with a tangent line of aboundary point of the curved center-edge surface and the curvedcentermost surface, they are intersected at an angle of 90 degrees.

It is also preferable that a boundary region of the curved center-edgesurface and the first curved circumferential surface may be placedwithin about 20 degrees to about 50 degrees with respect to the centerof the base. The curved centermost surface may be a cone-shaped groove.

According to another embodiment of the present invention, there isprovided an LED comprising: a first lens including a base, a firstcurved circumferential surface upwardly extending from the base, and afirst curved central surface; and a light emitting chip provided underthe first lens.

Here, it is preferable that a distance from a point of an upper surfaceof the light emitting chip to a point of the first curved centralsurface is shorter than the radius of curvature for the correspondingpoint of the first curved central surface.

The LED further comprises a central hollow portion upwardly formed fromthe base of the first lens. The central hollow portion includes a secondcurved circumferential surface and a second curved central surfaceextending from the second curved circumferential surface, which areinner surfaces of the first lens. Here, it is preferable that a distancefrom a point of an upper surface of the light emitting chip to a pointof the second curved central surface is longer than the radius ofcurvature for the corresponding point of the second curved centralsurface.

The LED further comprises a second lens which is provided in the centralhollow portion of the first lens to cover the light emitting chip. Thesecond lens includes a base, a third curved circumferential surfaceupwardly extending from the base, and a third curved central curvedextending from the third curved circumferential surface. In this lens,it is preferable that a distance from a point of an upper surface of thelight emitting chip to a point of the third curved central surface isshorter than the radius of curvature for a corresponding point of thethird curved central surface.

The LED further comprises a central hollow portion upwardly formed fromthe base of the second lens. The central hollow portion includes afourth curved circumferential surface and a fourth curved centralsurface extending from the fourth curved circumferential surface, whichare inner surfaces of the lens. In the second lens, it is preferablethat a distance from a point of an upper surface of the light emittingchip to a point of the fourth curved central surface is longer than theradius of curvature for the corresponding point of the fourth curvedcentral surface.

The second lens is formed with a material having a refractive index ofn, and it includes a base, a fifth curved circumferential surfaceupwardly extending from the base, a curved center-edge surface extendingfrom the fifth curved circumferential surface, and a curved centermostsurface extending from the curved center-edge surface. A groove isformed at the center of the base for receiving the light emitting chiptherein.

In the second lens, it is preferable that a distance from a point of anupper surface of the light emitting chip to a point of the curvedcenter-edge surface is shorter than the radius of curvature for thecorresponding point of the curved center-edge surface, and the curvedcentermost surface has a concave shape when viewed from the lightemitting chip.

The LED further comprises a central hollow portion upwardly formed fromthe base of the second lens. The central hollow includes a sixth curvedcircumferential surface and a sixth curved central surface extendingfrom the sixth curved circumferential surface, which are inner surfacesof the second lens. Here, it is preferable that a distance from a pointof an upper surface of the light emitting chip to a point of the sixthcurved central surface is longer than the radius of curvature for thecorresponding point of the sixth curved central surface.

The LED further comprises a supporting unit which is attached to thebase of the first lens for supporting the light emitting chip thereon.

According to another embodiment of the present invention, there isprovided an LED comprised of: a first lens which is formed with amaterial having a refractive index of n, and the lens includes a base, afirst curved circumferential surface upwardly extending from the base, afirst curved center-edge surface extending from the first curvedcircumferential surface, and a first curved centermost surface extendingfrom the first curved center-edge surface; and a light emitting chipwhich is provided under the first lens.

In this LED, a distance from a point of an upper surface of the lightemitting chip to a point of the first curved center-edge surface isshorter than the radius of curvature for the corresponding point of thefirst curved center-edge surface. The first curved centermost surfacehas a concave shape when viewed from the light emitting chip.

Here, it is preferable that the LED is constructed to satisfy thefollowing equation:A1+A2<90+sin⁻¹(1/n),

wherein A1 is an obtuse angle formed between the main axis of the firstlens and a tangent line of a point of the first curved centermostsurface, and A2 is an acute angle formed between a straight line linkingthe center of the base to the corresponding point of the first curvedcentermost surface and the main axis of the first lens.

The LED further comprises a central hollow portion upwardly formed fromthe base of the first lens. The central hollow portion includes a secondcurved circumferential surface and a first curved central surfaceextending from the second curved circumferential surface, which areinner surfaces of the first lens. Here, it is preferable that a distancefrom a point of an upper surface of the light emitting chip to a pointof the first curved central surface is longer than the radius ofcurvature for the corresponding point of the first curved centralsurface.

The LED further comprises a second lens which is provided in the centralhollow portion of the first lens to cover the light emitting chip. Thesecond lens includes a base, a third curved circumferential surfaceupwardly extending from the base, and a second curved central surfaceextending from the third curved circumferential surface.

Here, it is preferable that a distance from a point of an upper surfaceof the light emitting chip to a point of the second curved centralsurface is shorter than the radius of curvature for the correspondingpoint of the second curved central surface.

The LED further comprises a central hollow portion upwardly formed fromthe base of the second lens. The central hollow portion includes afourth curved circumferential surface and a third curved central surfaceextending from the fourth curved circumferential surface, which areinner surfaces of the second lens.

Here, it is also preferable that a distance from a point of an uppersurface of the light emitting chip to a point of the third curvedcentral surface is longer than the radius of curvature for thecorresponding point of the third curved central surface.

The second lens is formed with a material having a refractive index ofn, and the second lens includes a base, a fifth curved circumferentialsurface upwardly extending from the base, a second curved center-edgesurface extending from the fifth curved circumferential surface, and asecond curved centermost surface extending from the second curvedcenter-edge surface.

Here, it is preferable that a distance from a point of an upper surfaceof the light emitting chip to a point of the second curved center-edgesurface is shorter than the radius of curvature for the correspondingpoint of the second curved center-edge surface, and the second curvedcentermost surface has a concave shape when viewed from the lightemitting chip.

The LED further comprises a central hollow portion upwardly formed fromthe base of the second lens. The central hollow portion is comprised ofa sixth curved circumferential surface and a fourth curved centralsurface extending from the sixth curved circumferential surface, whichare inner surfaces of the second lens.

Here, it is preferable that a distance from a point of an upper surfaceof the light emitting chip to a point of the fourth curved centralsurface is longer than the radius of curvature for the correspondingpoint of the fourth curved central surface.

The LED further comprises a supporting unit which is attached to thebase of the first lens for supporting the light emitting chip thereon.

In this LED, the first curved centermost surface is a cone-shapedgroove.

According to another embodiment of the present invention, there isprovided an LED which comprises: a lens including a base, a first curvedcircumferential surface upwardly extending from the base, and a firstcurved central surface; and a light emitting chip provided under thelens.

In this LED, at least a partial area of the first curved central surfaceand the first curved circumferential surface includes an uneven pattern.Here, it is preferable that a distance from a point of an upper surfaceof the light emitting chip to a point of an outline of the first curvedcentral surface is shorter than the radius of curvature for thecorresponding point of the outline surface of the first curved centralsurface.

The LED further comprises a central hollow portion upwardly formed fromthe base of the lens. The central hollow portion includes a secondcurved circumferential surface and a second curved central surfaceextending from the second curved circumferential surface, which areinner surfaces of the lens. Here, it is preferable that a distance froma point of an upper surface of the light emitting chip to a point of thesecond curved central surface is longer than the radius of curvature forthe corresponding point of the second curved central surface.

The LED further comprises an inner lens which is provided in the centralhollow portion of the lens to cover the light emitting chip. The innerlens includes a base, a curved circumferential surface upwardlyextending from the base, and a curved central surface extending from thecurved circumferential surface.

Here, it is preferable that a distance from a point of an upper surfaceof the light emitting chip to a point of the curved central surface isshorter than the radius of curvature for the corresponding point of thecurved central surface.

In the LED, the uneven pattern is formed at the boundary area of thefirst curved central surface and the first curved circumferentialsurface.

According to another embodiment of the present invention, there isprovided an LED which comprises: a lens which is formed with a materialhaving a refractive index of n, and it includes a base, a first curvedcircumferential surface upwardly extending from the base, a curvedcentral-edge surface extending from the first curved circumferentialsurface, and a curved centermost surface extending from the curvedcentral-edge surface; and a light emitting chip which is provided underthe lens.

In the LED, at least a partial area of the curved centermost surface,the curved central-edge surface and the first curved circumferentialsurface includes an uneven pattern. Here, it is preferable that adistance from a point of an upper surface of the light emitting chip toa point of the curved central-edge surface is shorter than the radius ofcurvature for the corresponding point of an outline surface of thecurved central-edge surface, and the curved centermost surface has aconcave shape when viewed from the light emitting chip.

Here, it is preferable that the LED is constructed to satisfy thefollowing equation:A1+A2<90+sin⁻¹(1/n),

wherein A1 is an obtuse angle formed between the main axis of the lensand a tangent line of a point of the curved centermost surface, and A2is an acute angle formed between a straight line linking the center ofthe base to the corresponding point of the curved centermost surface andthe main axis of the lens.

The LED further comprises a central hollow portion upwardly formed fromthe base of the lens. The central hollow portion includes a secondcurved circumferential surface and a curved central surface upwardlyextending from the second curved circumferential surface, which areinner surfaces of the lens.

Here, it is preferable that a distance from a point of an upper surfaceof the light emitting chip to a point of the curved central surface islonger than the radius of curvature for the corresponding point of thecurved central surface.

The LED further comprises an inner lens which is provided in the centralhollow portion of the lens to cover the light emitting chip. The innerlens includes a base, a curved circumferential surface upwardlyextending from the base, and a curved central surface extending from thecurved circumferential surface. Here, it is preferable that a distancefrom a point of an upper surface of the light emitting chip to a pointof the curved central surface is shorter than the radius of curvaturefor the corresponding point of the curved central surface.

In the LED, the uneven pattern may be formed at the boundary area of thecurved centermost surface and the curved center-edge surface and theboundary area of the curved center-edge surface and the first curvedcircumferential surface. The curved centermost surface may be acone-shaped groove.

According to another embodiment of the present invention, there isprovided an LED which comprises a lens including a base, a first curvedcircumferential surface upwardly extending from the base, and a firstcurved central surface.

In this LED, an acute angle formed between a straight line linking thecenter of the base to a point of the first curved central surface andthe main axis of the lens is larger than an acute angle formed betweenthe normal for the corresponding point of the first curved surface andthe main axis of the lens.

The LED further comprises a central hollow portion upwardly formed fromthe base of the lens. The central hollow portion is comprised of asecond curved circumferential surface and a second curved centralsurface extending from the second curved circumferential surface, whichare inner surfaces of the lens.

Here, it is preferable that an acute angle formed between a straightline linking the center of the base to a point of the second curvedcentral surface and the main axis of the lens is smaller than an acuteangle formed between the normal for the corresponding point of thesecond curved central surface and the main axis of the lens.

According to another embodiment of the present invention, there isprovided a lens for an LED, which is formed with a material having arefractive index of n, and is comprised of: a base; a first curvedcircumferential surface upwardly extending from the base; a curvedcenter-edge surface extending from the first curved circumferentialsurface; and a curved centermost surface extending from the curvedcentral-edge surface.

Here, it is preferable that an acute angle formed between a straightline linking the center of the base to a point of the curved center-edgesurface and the main axis of the lens is larger than an acute angleformed between the normal for the corresponding point of the curvedcenter-edge surface and the main axis of the lens, and the curvedcentermost surface has a concave shape when viewed from the base.

Here, it is preferable that the lens is constructed to satisfy thefollowing equation:A1+A2<90+sin⁻¹(1/n),

wherein A1 is an obtuse angle formed between the main axis of the lensand a tangent line of a point of the curved centermost surface, and A2is an acute angle formed between a straight line linking the center ofthe base to the corresponding point of the curved centermost surface andthe main axis of the lens.

The lens further comprises a central hollow portion upwardly formed fromthe base of the lens. The central hollow portion is comprised of asecond curved circumferential surface and a curved central surfaceextending from the second curved circumferential surface, which areinner surfaces of the lens.

Here, it is preferable that an acute angle formed between a straightline linking the center of the base to a point of the curved centralsurface and the main axis of the lens is smaller than an acute angleformed between the normal for the corresponding point of the curvedcentral surface and the main axis of the lens.

According to another embodiment of the present invention, a lens for alight emitting diode comprises a base, a first curved surface extendingfrom the base, and a second curved surface extending from the firstcurved surface, wherein a distance from a center of the base to a pointof the second curved surface is shorter than a radius of curvature forthe point of the first curved central surface.

The lens may include a hollow portion formed from the base,

wherein the hollow portion is comprised of a third curved surface and afourth curved surface extending from the third curved surface, andwherein a distance from the center of the base to a point of the fourthcurved surface is longer than the radius of curvature for the point ofthe fourth curved surface.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention can be understood in moredetail from the following descriptions taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a block diagram of an LCD according to an embodiment of thepresent invention.

FIG. 2 is an exploded perspective view schematically illustrating an LCDaccording to an embodiment of the present invention.

FIG. 3 is an equivalent circuit view of a pixel unit of an LCD accordingto an embodiment of the present invention.

FIG. 4 is a perspective view of a light emitting diode according to anembodiment of the present invention.

FIG. 5 is a cross-sectional view of the light emitting diode of FIG. 4.

FIG. 6 is a reference view for illustrating the refraction of light atthe surface of a lens of the light emitting diode of FIG. 4.

FIG. 7 is a perspective view of a light emitting diode according to anembodiment of the present invention.

FIG. 8 is a cross-sectional view of the light emitting diode of FIG. 7.

FIG. 9 is a cross-sectional view of a light emitting diode according toan embodiment of the present invention.

FIG. 10 is a cross-sectional view of a light emitting diode according toan embodiment of the present invention.

FIG. 11 is a perspective view of a light emitting diode according to anembodiment of the present invention.

FIG. 12 is a cross-sectional view of the light emitting diode of FIG.11.

FIG. 13 is a reference view for illustrating the refraction of light atthe surface of a lens of the light emitting diode of FIG. 11.

FIG. 14 through FIG. 18 are cross-sectional views of light emittingdiodes according to embodiments of the present invention.

FIG. 19 through FIG. 24 are cross-sectional views showing LEDs accordingto embodiments of the present invention.

FIG. 25 is a graph showing flux to the incident angle of light raysemitted from LEDs according to embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be describedmore fully hereinafter with reference to the accompanying drawings, inwhich preferred embodiments of the invention are shown. The presentinvention may, however, be embodied in different forms and should not beconstrued as being limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the invention to thoseskilled in the art.

In the drawings, the thickness of the layers, films, and regions areexaggerated for clarity. Like numerals refer to like elementsthroughout. It will be understood that when an element such as a layer,film, region, or substrate is referred to as being “on” another element,it can be directly on the other element or intervening elements may alsobe present.

Hereinafter, a light source device for a display device according topreferred embodiments of the present invention will be described indetail with reference to the accompanying drawings.

FIG. 1 is a block diagram of an LCD according to an embodiment of thepresent invention, FIG. 2 is an exploded perspective view schematicallyillustrating an LCD according to an embodiment of the present invention,and FIG. 3 is an equivalent circuit view of pixel unit of an LCDaccording to an embodiment of the present invention.

Referring to FIG. 1, an LCD according to an embodiment of the presentinvention comprises an LC panel assembly 300, a gate driver 400 and adata driver 500 which are connected to the LC panel assembly 300, a grayvoltage generator 800 connected to the data driver 400, a light sourcesection 910 for supplying light to the LC panel assembly 300, a lightsource driver 920 for controlling the light source section 910, and asignal controller 600 for controlling the above elements.

Referring to FIG. 2, the LCD configuration according to an embodiment ofthe present invention comprises an LC module 350 including a displayunit 330 and a back light 340, a front housing 361 and a rear housing362 for receiving and supporting the LC module 350, and mold frames 363and 364.

The display unit 330 includes the LC panel assembly 300, a gate tapecarrier package (TCP) 410 and a data TCP 510 which are attached to theLC panel assembly 300, and a gate printed circuit board (PCB) 450 and adata PCB 550 which are individually attached to the corresponding TCPs410 and 510.

In a structural view shown in FIG. 2 and FIG. 3, the LC panel assembly300 includes a lower panel 100 and an upper panel 200 facing each other,and an LC layer 3 interposed therebetween. In an equivalent circuitshown in FIG. 1 and FIG. 3, the LC panel assembly 300 includes aplurality of display signal lines G₁-G_(n) and D₁-D_(m) and a pluralityof pixels connected thereto and arranged substantially in a matrix.

The display signal lines G₁-G_(n) and D₁-D_(m) are provided on the lowerpanel 100 and include a plurality of gate lines G₁-G_(n) fortransmitting gate signals (also referred to as “scanning signals”), anda plurality of data lines D₁-D_(m) for transmitting data signals. Thegate lines G₁-G_(n) extend substantially in a row direction andsubstantially parallel to each other, while the data lines D₁-D_(m)extend substantially in a column direction and substantially parallel toeach other.

Each pixel includes a switching element Q which are connected to thedisplay signal lines G₁-G_(n) and D₁-D_(m), and an LC capacitor C_(LC)and a storage capacitor C_(ST) which are connected to the switchingelement Q. The storage capacitor C_(ST) may be omitted.

The switching element Q such as a thin film transistor (TFT) is providedon the lower panel 100 and has three terminals: a control terminalconnected to one of the gate lines G₁-G_(n); an input terminal connectedto one of the data lines D₁-D_(m); and an output terminal connected toboth of the LC capacitor C_(LC) and the storage capacitor C_(ST).

The LC capacitor C_(LC) includes a pixel electrode 190 provided on thelower panel 100 and a common electrode 270 provided on the upper panel200 as two terminals. The LC layer 3 interposed between the twoelectrodes 190 and 270 functions as a dielectric for the LC capacitorC_(LC). The pixel electrode 190 is connected to the switching element Q,and the common electrode 270 is supplied with a common voltage V_(com)and covers the entire surface of the upper panel 200. Alternatively, thecommon electrode 270 may be provided on the lower panel 100. At leastone of the pixel electrode 190 and the common electrode 270 may beshaped as a bar or a stripe.

The storage capacitor C_(ST) is an auxiliary capacitor for the LCcapacitor C_(LC). When the pixel electrode 190 and a separate signalline (not shown) which is provided on the lower panel 100 are overlappedwith each other, interposing an insulator therebetween, the overlappedportion becomes the storage capacitor C_(ST). The separate signal lineis supplied with a predetermined voltage such as the common voltageV_(com). Alternatively, the storage capacitor C_(ST) may be formed byoverlapping of the separate signal line with a pixel electrode of theprevious gate line which is placed directly before the pixel electrode190, and interposing an insulator therebetween.

For color display, each pixel uniquely exhibits one of three primarycolors (i.e., spatial division), or sequentially exhibits three primarycolors in turn depending on time (i.e., temporal division), so that aspatial or temporal sum of the primary colors are recognized as adesired color. FIG. 3 shows an example of the spatial division in whicheach pixel includes a color filter 230 for exhibiting one of the primarycolors in an area of the upper panel 200 corresponding to the pixelelectrode 190. Alternatively, the color filter 230 may be provided on orunder the pixel electrode 190 of the lower panel 100.

Referring to FIG. 2, the backlight 340 is mounted under the LC panelassembly 300. The backlight 340 comprises a light source unit 349including a printed circuit board (PCB) 345 and a plurality of lightemitting diodes (LEDs) 344 mounted thereon, and a light guiding plate342 and a plurality of optical sheets 343 which are provided between theLC panel assembly 300 and the LEDs 344 for dispersing the light from theLEDs 344 to the LC panel assembly 300. The backlight 340 furthercomprises a reflecting plate 341 which is provided on the PCB 345 forreflecting the light from the LEDs 344 toward the LC panel assembly 300,and includes a plurality of holes where light emitting chips of the LEDs344 are protruded therethrough. The backlight 340 further comprises amold frame 364 which is provided between the reflecting plate 341 andthe light guiding plate 342 for maintaining a regular interval betweenthe light source unit 349 and the light guiding plate 342 and forsupporting the light guiding plate 342 and the optical sheets 343.

The LEDs 344 as the light source may be white light emitting diodes or acombination of red, green, and blue light emitting diodes. The red lightemitting diode, etc. can be used as an auxiliary diode for the whitelight emitting diode. The LEDs 344 are arranged on the PCB 345 in apredetermined form, thereby forming the light source unit 349.

FIG. 2 shows three light source units 349, but the number of the lightsource units 349 can be varied depending on required brightness, screensize of the LCD, etc.

Polarizers (not shown) are provided on the outer surfaces of the twopanels 100 and 200 for polarizing the light emitted from the lightsource units 349.

Referring to FIG. 1 and FIG. 2, the gray voltage generator 800 isincluded in the data PCB 550 and generates two sets of a plurality ofgray voltages related to the transmittance of the pixels. The grayvoltages in one set have a positive polarity with respect to the commonvoltage V_(com), while those of the other set have a negative polaritywith respect to the common voltage V_(com).

The gate drivers 400 are individually mounted on each gate TCP 410,having the shapes of an integrated circuit (IC) chip, and areindividually connected to the gate lines G₁-G_(n) of the LC panelassembly 300 for transmitting the gate signals consisting ofcombinations of the gate-on voltage V_(on) and the gate-off voltageV_(off) input from an external device to the gate signal lines G₁-G_(n).

The data drivers 500 are individually mounted on each data TCP 510,having the shapes of IC chips, and are individually connected to thedata lines D₁-D_(m) of the LC panel assembly 300 for transmitting thedata voltages which are selected from the gray voltages supplied fromthe gray voltage generator 800 to the data signal lines D₁-D_(m).

In another embodiment of the present invention, the gate driver 400 orthe data driver 500 is directly mounted on the lower panel 100, havingthe shape of an IC chip, and in still another embodiment of the presentinvention, the gate driver 400 or the data driver 500 is integrated intothe lower panel 100 along with other elements. In the above cases, thegate PCB 450 or the gate TCP 410 can be omitted.

The signal controller 600 is included in the data PCB 550 or the gatePCB 450 for controlling the operation of the gate driver 400 or the datadriver 500.

Hereinafter, the operation of the above-mentioned LCD will be described.

The signal controller 600 receives input image signals R, G, and B andinput control signals for controlling the display thereof such as avertical synchronizing signal V_(sync), a horizontal synchronizingsignal H_(sync), a main clock MCLK, a data enable signal DE, etc. froman external graphic controller (not shown). In response to the inputimage signals R, G, and B and the input control signals, the signalcontroller 600 processes the image signals R, G, and B suitably for theoperation of the LC panel assembly 300 and generates gate controlsignals CONT1 and data control signals CONT2, and then outputs the gatecontrol signals CONT1 and the data control signals CONT2 to the gatedriver 400 and the data driver 500, respectively.

The gate control signals CONT1 include a vertical synchronizing startsignal STV for indicating the beginning of a frame, a gate clock signalCPV for controlling the output time of the gate-on voltage V_(on), andan output enable signal OE for defining the duration of the gate-onvoltage V_(on).

The data control signals CONT2 include a horizontal synchronizing startsignal STH for indicating the beginning of data transmission, a loadsignal LOAD for instructing to apply the data voltages to the data linesD₁-D_(m), a reverse signal RVS for reversing the polarity of the datavoltages with respect to the common voltage V_(com), and a data clocksignal HCLK.

Responsive to the data control signals CONT2 from the signal controller600, the data driver 500 successively receives the image data DAT for arow of the pixels from the signal controller 600, shifts them, convertsthe image data DAT into analog data voltages selected from the grayvoltages from the gray voltage generator 800, and then applies the datavoltages to data lines D₁-D_(m).

The gate driver 400 applies the gate-on voltage Von to the gate linesG₁-G_(n) in response to the gate control signals CONT1 from the signalcontroller 600, and thereby turns on the switching elements Q connectedthereto. The data voltages applied to the data lines D₁-D_(m) areapplied to the corresponding pixel through the activated switchingelements Q.

The difference between the data voltage applied to the pixel and thecommon voltage V_(com) is represented as a voltage across the LCcapacitor C_(LC), namely, a pixel voltage. The LC molecules in the LCcapacitor C_(LC) have orientations depending on the magnitude of thepixel voltage.

The light source driver 920 controls current applied to the light sourcesection 910 for switching the LED 344 of the light source section 910,and also controls the brightness of the light from the LED 344.

When the light emitted from the LED 344 passes through the LC layer 3,the polarization of the light is varied according to the orientations ofthe LC molecules. The polarizer converts the difference of the lightpolarization into a difference of the light transmittance.

By repeating this procedure by a unit of the horizontal period (which isdenoted by “1H” and is equal to one period of the horizontalsynchronizing signal H_(sync), the data enable signal DE, and the gateclock CPV), all gate lines G₁-G_(n) are sequentially supplied with thegate-on voltage V_(on) during a frame, thereby applying the datavoltages to all pixels. When the next frame starts after finishing oneframe, the reverse control signal RVS applied to the data driver 500 iscontrolled such that the polarity of the data voltages is reversed withrespect to that of the previous frame (which is referred to as “frameinversion”). The reverse control signal RVS may be also controlled suchthat the polarity of the data voltages flowing in a data line in oneframe are reversed (for example, line inversion and dot inversion), orthe polarity of the data voltages in one packet are reversed (forexample, column inversion and dot inversion).

Hereinafter, an LED for a backlight device according to an embodiment ofthe present invention will be described with reference to FIG. 4, FIG.5, and FIG. 6.

FIG. 4 is a perspective view of an LED according to an embodiment of thepresent invention. FIG. 5 is a cross-sectional view of the LED of FIG.4. FIG. 6 is a reference view for illustrating the refraction of lightat the surface of a lens of the LED of FIG. 4.

Referring to FIG. 4 and FIG. 5, an LED 344 comprises a light emittingchip 4 and a lens. The lens is made of a transparent dielectric materialand includes a base 31, a curved circumferential surface 2 which extendsfrom the base 31, and a curved central surface 1 which extends from thecurved circumferential surface 2. The base 31 has a groove for receivingthe light emitting chip 4 therein.

It is preferable that the curved central surface 1 of the lens has aconvex shape when viewed from the light emitting chip 4, and issymmetrical with respect to a lens axis which vertically extends fromthe center of the light emitting chip 4. In the lens shown in FIGS. 4and 5, a distance, for example d₁, d₂ or d₃ from a point A of the lightray emitting surface of the light emitting chip 4 to a point, forexample P₁, P₂, P₃, of the curved central surface 1 is always shorterthan the radius of curvature r (of osculating circle C) for thecorresponding point of the curved central surface 1. The osculatingcircle C at, for example, point P₁ has the same tangent t₁ as the curvedcentral surface 1 at point P₁. This condition is hereinafter referred toas “the first condition of the radius of curvature” and results inuniform dispersion of the light ray emitted from the light emitting chip4 to a wider area.

While only considering the lens, it is preferable that a distance fromthe center of the base 31 to a point of the curved central surface 1 isalways shorter than the radius of curvature for the corresponding pointof the curved central surface 1. This condition is hereinafter referredto as “the modified first condition of the radius of curvature”.Otherwise, referring to FIG. 6, it is preferable to construct a lens sothat an acute angle B1 formed between a line linking the center of thebase 31 to a point P of the curved central surface 1 and the main axisof the lens (“Lens axis” in FIG. 6) is always larger than an acute angleB2 formed between a normal for the corresponding point of the curvedcentral surface 1 and the main axis of the lens. This condition ishereinafter referred to as “the first condition of light dispersion”.

The shape of the curved circumferential surface 2 results by steeplycutting the side of the lens, so that the size of the lens is reducedand incident light which excessively slants toward the side of the lensis redirected to the upper direction of the lens. However, if necessary,the lens may be constructed so that the curved circumferential surface 2satisfies the first condition of the radius of curvature or the firstcondition of light dispersion. That is, the lens may be constructed insuch a way that the curved central surface 1 extends to the base 31,omitting the curved circumferential surface 2.

The radius of curvature is more abruptly changed at the boundary area ofthe curved central surface 1 and the curved circumferential surface 2 ascompared with at the curved central surface 1 or at the curvedcircumferential surface 2, and therefore it may be discontinuous. Adiscontinuous radius of curvature brings a discontinuous lightdistribution. Therefore, it is preferable to trim the boundary cornerfor a continuous variation of the radius of curvature. It is alsopreferable that the position of the boundary of the curved centralsurface 1 and the curved circumferential surface 2 is controlleddepending on the light emitting distribution. For example, the boundaryof the curved central surface 1 and the curved circumferential surface 2is placed at an angle between about 20 degrees and about 50 degrees fromthe center of the groove for receiving the light emitting chip 4. Thatis, since the light ray emitted from the light emitting chip 4 iscondensed within an angle between about 20 degrees and about 50 degreesfrom the center of the groove and is rarely distributed beyond thatrange, it is enough that the lens is formed in order that the curvedcentral surface 1 covers the light condensed region.

In a lens satisfying the first condition of the radius of curvature orthe first condition of light dispersion, the light ray emitted from thelight emitting chip 4 is always refracted in a receding direction fromthe main axis of the lens. This will be described with reference to FIG.6.

If the lens satisfies the first condition of the radius of curvature orthe first condition of light dispersion, when the wave plane of thelight meets the curved central surface 1 as shown in FIG. 6, the waveplane near the main axis of the lens first enters into the air beforepassing through the lens. As a result, the incident light is refractedin the receding direction from the main axis of the lens due to thedifference of the speed of the light in air and in the lens.

FIG. 7 is a perspective view of an LED according to an embodiment of thepresent invention, and FIG. 8 is a cross-sectional view of the LED ofFIG. 7.

As compared to that of the embodiment described in connection with FIGS.4-6, this LED further comprises a central hollow portion upwardly formedfrom a base 31, and a supporting unit 7 provided on the base 31 forsupporting a light emitting chip 4 thereon.

The central hollow portion comprises a curved central surface 5 and acurved circumferential surface 6 which are the inner surface of thelens. It is preferable that the curved central surface 5 of the centralhollow portion has a convex shape when viewed from the light emittingchip 4 and is symmetrical with respect to the main axis of the lens,which vertically extends from the center of the light emitting chip 4.In this lens, a distance from a point of the light emitting surface ofthe light emitting chip 4 to a point of the curved central surface 5 isalways longer than the radius of curvature for the corresponding pointof the curved central surface 5. This condition is hereinafter referredto as “the second condition of the radius of curvature” and results inuniform dispersion of the light ray emitted from the light emitting chip4 to a wider region.

While only considering the lens, it is preferable that a distance fromthe center of the base 31 to a point of the curved central surface 5 ofthe central hollow portion is always longer than the radius of curvaturefor the corresponding point of the curved central surface 5 of thecentral hollow portion. This condition is hereinafter referred to as“the modified second condition of the radius of curvature”. Otherwise,it is preferable to construct the lens so that an acute angle formedbetween a straight line linking the center of the base 31 to a point ofthe curved central surface 5 of the central hollow portion and the mainaxis of the lens is always smaller than an acute angle formed betweenthe normal for the corresponding point of the curved central surface 5of the central hollow portion and the main axis of the lens. Thiscondition is hereinafter referred to as “the second condition of lightdispersion”.

The supporting unit 7 is attached to the base 31 for receiving the lightemitting chip 4 therein. It is preferable that the supporting unit 7 isattached to the base 31 so as to not close the bottom opening of thecentral hollow portion. If the bottom opening were closed, the air inthe central hollow portion would expand by the heat generated when thelight emitting chip 4 is operating, causing the supporting unit 7 to beseparated from the lens.

When the curved central surface 5 of the central hollow portion isformed to satisfy the second condition of the radius of curvature or thesecond condition of light dispersion, the light ray emitted from thelight emitting chip 4 is always refracted in the receding direction fromthe main axis of the lens.

In accordance with the above, since the light ray emitted from the lightemitting chip 4 enters the lens passing through the air of the centralhollow portion, the curved central surface 5 of the central hollowportion should satisfy the condition of the radius of curvature or thecondition of light dispersion opposite to those for the curved centralsurface 1 of the lens for satisfactory light dispersion.

FIG. 9 is a cross-sectional view of an LED according to an embodiment ofthe present invention.

As compared to the embodiment shown in FIG. 4 and FIG. 5, this LEDfurther comprises an uneven pattern 8, which is formed at the curvedcentral surface 1 and the partial curved circumferential surface 2 ofthe lens. The uneven pattern 8 can be configured as a minute pattern.The uneven pattern 8 causes the light ray to disperse more uniformly. Itcan be formed at the entire curved central surface 1 and the entirecurved circumferential surface 2, or only at the boundary of the curvedcentral surface 1 and the curved circumferential surface 2.

FIG. 10 is a cross-sectional view of an LED according to an embodimentof the present invention.

As compared to that of the embodiment shown in FIG. 7 and FIG. 8, thisLED further comprises an uneven pattern 8 which is formed at theboundary of the curved central surface 1 and the curved circumferentialsurface 2. The uneven pattern 8 causes the light ray to disperse moreuniformly. It can be formed at the entire curved central surface 1 andthe entire curved circumferential surface 2, or only at specific areasof the curved central surface 1 and the curved circumferential surface2.

In the embodiments shown in FIG. 9 and FIG. 10, although the unevenpattern 8 is provided at the curved central surface 1 and the curvedcircumferential surface 2, an outline surface resulting by linking toppoints of the prominences of the uneven pattern 8 satisfies the firstcondition of the radius of curvature or the modified first condition ofthe radius of curvature or the first condition of light dispersion.

FIG. 11 is a perspective view of an LED according to an embodiment ofthe present invention, FIG. 12 is a cross-sectional view of the LED ofFIG. 11, and FIG. 13 is a reference view for illustrating the lightreflection at the surface of the lens for the LED of FIG. 11.

Referring to FIG. 11 and FIG. 12, an LED comprises a light emitting chip15 and a lens. The lens is formed with a transparent dielectric andincludes a base 14, a curved circumferential surface 13 which extendsfrom the base 14, a curved center-edge surface 12 which extends from thecurved circumferential surface 13, and a curved centermost surface 11which extends from the curved center-edge surface 12. The base 14 has agroove for receiving a light emitting chip 15.

It is preferable that the curved center-edge surface 12 of the lens hasa convex shape when viewed from the light emitting chip 15, and issymmetrical with respect to the main axis of the lens which verticallyextends from the center of the light emitting chip 15. In this lens, adistance from a point of the light emitting surface of the lightemitting chip 15 to a point of the curved center-edge surface 12 isalways shorter than the radius of curvature for the corresponding pointof the curved center-edge surface 12 of the lens (i.e., the firstcondition of the radius of curvature). This is to uniformly disperse thelight ray emitted from the light emitting chip 15 to a wider region.

While only considering the lens, it is preferable that a distance fromthe center of the base 14 to a point of the curved center-edge surface12 of the lens is always shorter than the radius of curvature for thecorresponding point of the curved center-edge surface 12 (i.e., themodified first condition of the radius of curvature). Otherwise, it ispreferable to construct the lens so that an acute angle formed between astraight line linking the center of the base 14 to a point of the curvedcenter-edge surface 12 of the central hollow and the main axis of thelens is always larger than an acute angle formed between the normal forthe corresponding point of the curved center-edge surface 12 and themain axis of the lens (i.e., the first condition of light dispersion).

It is preferable that the curved centermost surface 11 of the lens has aconcave shape when viewed from the light emitting chip 15 and issymmetrical with respect to the main axis of the lens which verticallyextends from the center of the light emitting chip 15. Also, the curvedcentermost surface 11 is formed to satisfy the following equation:A1+A2<90+sin⁻¹(1/n)   (Equation 1)

where n is a refraction index, A1 is an obtuse angle formed between themain axis of the lens and a tangent line of a point on the curvedcentermost surface 11, and A2 is an acute angle formed between a linelinking the center of the light emitting chip 15 to the correspondingpoint of the curved centermost surface 11 and the main axis of the lens.

When the curved centermost surface 11 satisfies the above equation, thelight ray emitted from the light emitting chip 15 is refracted at thecurved centermost surface 11 and then is dispersed without totalinternal reflection. In other words, most of the light ray from thelight emitting chip 15 is upwardly dispersed passing through the curvedcentermost surface 11 and the curved center-edge surface 12.

In this manner, since most of the light ray is directly dispersed upwardwithout the reflection, the light ray from the light emitting diode canbe efficiently used.

Hereinafter, the derivation of Equation 1 will be described withreference to FIG. 13.

In FIG. 13, Ai is the angle of incidence measured when the light rayemitted from the light emitting chip 15 is directed toward a point ofthe curved centermost surface 11, Ar is the angle of refraction, and nis the index of refraction. With these elements, Snell's Law isexpressed by the following equation:Sin Ar/Sin Ai=n/1   (Equation 2)

If a total internal reflection occurs, Ar is 90 degrees. Accordingly,the critical angle of incidence Ai is derived by the followingequations:Sin Ai=1/n   (Equation 3)Ai=Sin⁻¹(1/n)   (Equation 4)

Therefore, the condition that the total internal reflection does notoccur is expressed by the following equation:Ai<Sin⁻¹(1/n)   (Equation 5)

In FIG. 13, since the sum of the internal angles of a triangle is 180degrees, the following equation is given:A1+A2+A3=180 degrees   (Equation 6)

In FIG. 13, the following equation is also given:Ai+A3=90 degrees   (Equation 7)

From the equations 5, 6, and 7, Equation 1 is derived. That is, Equation1 means the condition that the total reflection of the light from thelight emitting chip 15 does not occur at the curved centermost surface11.

The shape of the circumferential curved surface 13 results from steeplycutting the side of the lens, so that the size of the lens is reducedand the incident light which excessively slants toward the side of thelens is redirected to the upper direction of the lens. If necessary, thelens may be constructed so that a distance from a point of the lightemitting surface of the light emitting chip 15 to a point of the curvedcircumferential surface 13 is always shorter than the radius ofcurvature for the corresponding point of the curved circumferentialsurface 13 of the lens. That is, the lens may be constructed in such away that the curved center-edge surface 12 extends until it reaches tothe base 14, omitting the formation of the curved circumferentialsurface 13.

The radius of curvature is more abruptly changed at the boundary of thecurved centermost surface 11 and the curved center-edge surface 12 andat the boundary of the curved center-edge surface 12 and the curvedcircumferential surface 13 as compared to at the curved centermostsurface 11, the curved center-edge surface 12, or the curvedcircumferential surface 13. The abrupt change in the radius of curvatureresults in a discontinuous radius of curvature, which causes adiscontinuous light distribution. Therefore, it is preferable to trimthe boundary corners for a continuous variation of the radius ofcurvature.

It is also preferable that the position of the boundary of the curvedcentermost surface 11 and the curved center-edge surface 12 and theposition of the boundary of the curved center-edge surface 12 and thecurved circumferential surface 13 are controlled depending on the lightemitting distribution. For example, the boundary of the curvedcenter-edge surface 12 and the curved circumferential surface 13 ispositioned at an angle between about 20 degrees and about 50 degreeswith respect to the center of the groove. That is, since the light rayemitted from the light emitting chip 15 is condensed within an anglebetween about 20 degrees and about 50 degrees to the center of thegroove and is rarely distributed beyond that range, it is enough thatthe lens is formed in order that the curved centermost surface 11 andthe curved center-edge surface 12 cover the light condensed region.

When the first curved centermost surface 11 satisfies Equation 1 and thecurved center-edge surface 12 satisfies the first condition of theradius of curvature, the light ray emitted from the light emitting chip15 is always refracted at the curved centermost surface 11 and thecurved center-edge surface 12 in the receding direction from the mainaxis of the lens.

FIG. 14 is a cross-sectional view of a light emitting diode according toan embodiment of the present invention.

As compared to that of the embodiment shown in FIG. 11 and FIG. 12, thislight emitting diode further comprises a central hollow portion upwardlyformed from a base 14, and a supporting unit 7 is attached to the base14 for supporting a light emitting chip 15 thereon.

The central hollow portion comprises a curved circumferential surface 17and a curved central surface 16, which form an inner surface of thelens. It is preferable that the curved central surface 16 of the centralhollow portion has a convex shape when viewed from the light emittingchip 15, and is symmetrical with respect to the main axis of the lenswhich vertically extends from the center of the light emitting chip 15.In this lens, a distance from a point of the light emitting surface ofthe light emitting chip 15 to a point of the curved central surface 16of the central hollow portion is always longer than the radius ofcurvature for the corresponding point of the curved central surface 16(i.e., the second condition of the radius of curvature). This is touniformly disperse the light ray emitted from the light emitting chip 15to a wider region.

While only considering the lens, it is preferable that a distance fromthe center of the base 14 to a point of the curved central surface 16 ofthe central hollow portion is always longer than the radius of curvaturefor the corresponding point of the curved central surface 16 (i.e., themodified second condition of the radius of curvature). Otherwise, it ispreferable to construct the lens so that an acute angle formed between astraight line linking the center of the base 14 to a point of the curvedcentral surface 16 of the central hollow portion and the main axis ofthe lens is always smaller than an acute angle formed between the normalfor the corresponding point of the curved central surface 16 and themain axis of the lens (i.e., the second condition of light dispersion).

A supporting unit 18 is attached to the base 14 for receiving the lightemitting chip 15 therein. Here, it is preferable that the supportingunit 18 is attached to the base 14 not so as to close a bottom openingof the central hollow portion. If the opening were closed, the air inthe central hollow portion would expand by the heat generated when thelight emitting chip 15 is operating, causing the supporting unit 18 toseparate from the lens.

If the central hollow portion is formed to satisfy the above-mentionedconditions, the light ray emitted from the light emitting chip 15 isalways refracted at the curved central surface 16 of the central hollowportion in the receding direction from the main axis of the lens.

FIG. 15 is a cross-sectional view of an LED according to an embodimentof the present invention.

As compared to that of the embodiment shown in FIG. 11 and FIG. 12, thisLED further comprises an uneven pattern 19 which is formed at the entirecurved centermost surface 11, the entire curved center-edge surface 12,and the partial curved circumferential surface 13 of the lens. Theuneven pattern 19 as a minute pattern. The uneven pattern 19 causes moreuniform dispersion of the light ray and can be formed at the entirecurved centermost surface 11, the entire curved center-edge surface 12,and the entire curved circumferential surface 13, or only at theboundary of the second central curved surface 12 and the curvedcircumferential surface 13.

FIG. 16 is a cross-sectional view of an LED according to an embodimentof the present invention.

As compared to that of the embodiment shown in FIG. 14, this LED furthercomprises uneven patterns 19 and 20 which are individually formed at theboundary of the curved centermost surface 11 and the curved center-edgesurface 12 and at the boundary of the curved center-edge surface 12 andthe circumferential curved surface 13. The uneven patterns 19 and 20cause more uniform dispersion of the light ray and can be configured asminute patterns. The uneven patterns 19 and 20 can be formed entirelyover the first central curved surface 11, the second central curvedsurface 12, and the circumferential curved surface 13, or only at thespecific areas of the first central curved surface 11, the secondcentral curved surface 12, and the circumferential curved surface 13.

In the embodiments shown in FIG. 15 and FIG. 16, although the unevenpatterns 19 and 20 are provided at the curved centermost surface 11, thecurved center-edge surface 12, and the curved circumferential surface13, an outline surface of the curved center-edge surface 12 (created bylinking top points of the prominences of the uneven patterns) satisfiesthe first condition of the radius of curvature or the modified firstcondition of the radius of curvature or the first condition of lightdispersion, and an outline surface of the curved centermost surface 11satisfies Equation 1.

FIG. 17 is a cross-sectional view of an LED according to an embodimentof the present invention.

As compared to that of the embodiment shown in FIG. 7 and FIG. 8, thisLED further comprises an inner lens 200 which covers a light emittingchip 4 in a central hollow portion. The inner lens 200 has the sameshape as the lens of light emitting diode shown in FIG. 4 and FIG. 5.That is, the inner lens 200 comprises a base, a curved circumferentialsurface that extends from the base, a curved central surface whichextends from the curved circumferential surface, and a groove which isprovided in the base for receiving the light emitting chip 4 therein.The curved central surface of the inner lens 200 satisfies the firstcondition of the radius of curvature or the first condition of lightdispersion. Also, the inner lens 200 may be formed in such a way thatthe curved central surface extends to the base, omitting the curvedcircumferential surface.

In the LED shown in FIG. 17, since the refraction is generated at theouter surface of the inner lens, the inner surface of outer lens, andthe outer surface of the outer lens, the light ray is dispersed to awider region.

FIG. 18 is a cross-sectional view of an LED according to an embodimentof the present invention.

As compared to that of the embodiment shown in FIG. 14, this LED furthercomprises an inner lens 200 which covers a light emitting chip 15 in acentral hollow portion. The inner lens 200 has the same shape as thelens of light emitting diode shown in FIG. 4 and FIG. 5. That is, theinner lens 200 comprises a base, a curved circumferential surface thatextends from the base, a curved central surface which extends from thecurved circumferential surface, and a groove which is provided in thebase of the inner lens 200 for receiving the light emitting chip 15therein. The curved central surface of the inner lens 200 satisfies thefirst condition of the radius of curvature or the first condition oflight dispersion. Also, the inner lens 200 may be formed in such a waythat the curved central surface extends to the base, omitting the curvedcircumferential surface.

In the LED shown in FIG. 18, since the refraction is generated at theouter surface of the inner lens, the inner surface of the outer lens,and the outer surface of the outer lens, the light ray is dispersed to awider region.

In the embodiments shown in FIG. 17 and FIG. 18, the inner lens has thesame shape as the lens of the light emitting diode shown in FIG. 4 andFIG. 5, but the shape of the inner lens can be varied. Hereinafter, suchvariations will be described.

Referring to FIG. 19, an LED includes an outer lens 101 and an innerlens 401. The outer lens 101 has the same shape as the lens of the LEDof FIG. 7 and FIG. 8. The inner lens 401 is provided in the centralhollow portion of the outer lens 101 and has a central hollow portion 9therein. A light emitting chip 4 is provided in the central hollowportion 9 of the inner lens 401. The inner lens 401 has the same shapeas the lens of the LED shown in FIG. 7 and FIG. 8. That is, the innerlens 401 comprises an outer surface, an inner surface defining thecentral hollow portion 9, and a base. The outer surface of the innerlens 401 comprises a curved circumferential surface and a curved centralsurface which satisfies the first condition of the radius of curvatureor the first condition of light dispersion, and the inner surfacecomprises a curved circumferential surface and a curved central surfacewhich satisfies the second condition of the radius of curvature or thesecond condition of light dispersion.

In the LED shown in FIG. 19, since the refraction is generated at theinner and outer surfaces of the inner lens, and at the inner and outersurfaces of the outer lens, the light ray is dispersed to a widerregion.

Referring to FIG. 20, an LED includes an outer lens 301 and an innerlens 401. The outer lens 301 has the same shape as the lens of the LEDof FIG. 14. The inner lens 401 is provided in the central hollow portionof the outer lens 301 and has a central hollow portion 9 therein. Alight emitting chip 15 is provided in the central hollow portion 9 ofthe inner lens 401. The inner lens 401 has the same shape as the lens ofthe LED shown in FIG. 7 and FIG. 8. That is, the inner lens 401comprises an outer surface, an inner surface defining the central hollowportion 9, and a base. The outer surface of the inner lens 401 comprisesa curved circumferential surface and a curved central surface thatsatisfies the first condition of the radius of curvature or the firstcondition of light dispersion. The inner surface of the inner lens 401comprises a curved circumferential surface and a curved central surfacethat satisfies the second condition of the radius of curvature or thesecond condition of light dispersion.

In the LED shown in FIG. 20, since the refraction is generated at theinner and outer surfaces of the inner lens, and at the inner and outersurfaces of outer lens, the light ray is dispersed to a wider region.

Referring to FIG. 21, an LED includes an outer lens 101 and an innerlens 601. The outer lens 101 has the same shape as the lens of the LEDof FIG. 7 and FIG. 8. The inner lens 601 is provided in the centralhollow portion of the outer lens 101 and covers a light emitting chip 4.The inner lens 601 has the same shape as the lens of the light emittingdiode shown in FIG. 11 and FIG. 12. That is, the inner lens 601 made ofa transparent dielectric comprises a base, a curved circumferentialsurface which extends from the base, a curved center-edge surface whichextends from the curved circumferential surface, and a curved centermostsurface which extends from the curved center-edge surface. A groove isprovided in the base of the inner lens 601 for receiving the lightemitting chip 4 therein. The curved center-edge surface of the innerlens 601 satisfies the first condition of the radius of curvature or thefirst condition of light dispersion, and the curved centermost surfacesatisfies Equation 1 relating to the condition that no total refractionis generated.

In the LED shown in FIG. 21, since the refraction is generated at theouter surface of the inner lens, and at the inner and outer surfaces ofthe outer lens, the light ray is dispersed to a wider region.

Referring to FIG. 22, an LED includes an outer lens 301 and an innerlens 601. The outer lens 301 has the same shape as the lens of the LEDshown in FIG. 14. The inner lens 601 is provided in the central hollowportion of the outer lens 301 and covers a light emitting chip 15. Theinner lens 601 has the same shape as the lens of the LED shown in FIG.11 and FIG. 12. That is, the inner lens 601 made of a transparentdielectric comprises a base, a curved circumferential surface thatextends from the base, a curved center-edge surface that extends fromthe curved circumferential surface, and a curved centermost surfacewhich extends from the curved center-edge surface. A groove is providedin the base of the inner lens 601 for receiving the light emitting chip15 therein. The curved center-edge surface of the inner lens 601satisfies the first condition of the radius of curvature or the firstcondition of light dispersion, and the curved centermost surfacesatisfies Equation 1 relating to the condition that no total refractionis generated.

In the LED shown in FIG. 22, since the refraction is generated at theouter surface of the inner lens, and at the inner and outer surfaces ofouter lens, the light ray is dispersed to a wider region.

Referring to FIG. 23, an LED includes an outer lens 101 and an innerlens 801. The outer lens 101 has the same shape as the lens of the LEDshown in FIG. 7 and FIG. 8. The inner lens 801 is provided in thecentral hollow portion of the outer lens 101 and has a central hollowportion 22 therein. A light emitting chip 4 is provided in the centralhollow portion 22 of the inner lens 801. The inner lens 801 has the sameshape as the lens of the LED shown in FIG. 14. That is, the inner lens801 comprises an outer surface, an inner surface defining the centralhollow portion 22, and a base. The outer surface of the inner lens 801comprises a curved circumferential surface, a curved center-edge surfacewhich satisfies the first condition of the radius of curvature or thefirst condition of light dispersion, and a curved centermost surfacewhich satisfies Equation 1 relating to the condition that no totalrefraction is generated, and the inner surface of the inner lens 801comprises a curved circumferential surface and a curved central surfacewhich satisfies the second condition of the radius of curvature or thesecond condition of light dispersion.

In the LED shown in FIG. 23, since the refraction is generated at theinner and outer surfaces of the inner lens, and at the inner and outersurfaces of the outer lens, the light ray is dispersed to a widerregion.

Referring to FIG. 24, an LED includes an outer lens 301 and an innerlens 801. The outer lens 301 has the same shape as the lens of the LEDshown in FIG. 14. The inner lens 801 is provided in the central hollowportion of the outer lens 301 and has a central hollow portion 22therein. A light emitting chip 15 is provided in the central hollowportion 22 of the inner lens 801. The inner lens 801 has the same shapeas the lens of the LED shown in FIG. 14. That is, the inner lens 801comprises an outer surface, an inner surface defining the central hollowportion 22, and a base. The outer surface of the inner lens 801comprises a curved circumferential surface, a curved center-edge surfacethat satisfies the first condition of the radius of curvature or thefirst condition of light dispersion, and a curved centermost surfacethat satisfies Equation 1 relating to the condition that no totalrefraction is generated. The inner surface of the inner lens 801comprises a curved circumferential surface and a curved central surfacethat satisfies the second condition of the radius of curvature or thesecond condition of light dispersion.

In the LED shown in FIG. 24, since the refraction is generated at theinner and outer surfaces of the inner lens, and at the inner and outersurfaces of the outer lens, the light ray is dispersed to a widerregion.

The above-mentioned embodiments of the LED are examples, and morevariations can be given. For example, the formation of the unevenpattern can be further varied.

FIG. 25 is a graph showing the flux to the incident angle of the lightray from the LEDs according to embodiments of the present invention.

In FIG. 25, curve C0 is the flux to the incident angle of the light rayemitted from the LED shown in FIG. 4 and FIG. 5, curve C1 is the flux tothe incident angle of the light ray emitted from the LED shown in FIG. 7and FIG. 8, curve C2 is the flux to the incident angle of the light rayemitted from the LED shown in FIG. 11 and FIG. 12, and curve C3 is theflux to the incident angle of the light ray emitted from the LED shownin FIG. 14. The flux is measured at 20 mm above the LED.

As shown in FIG. 25, the dispersion of the light ray is enlarged in theorder of the embodiment shown in FIG. 4 and FIG. 5, the embodiment shownin FIG. 7 and FIG. 8, the embodiment shown in FIG. 11 and FIG. 12, andthe embodiment shown in FIG. 14.

As the incident angle of the light ray emitted from the LED increases,the RGB mixing section for producing the white light and the uniformdispersion section for producing the uniform surface light can beminimized.

Accordingly, an LED according to embodiments of the present inventioncan widen the three-dimensional incident angle, and thus the RGB mixingsection for producing the white light and the uniform dispersion sectionfor emitting the uniform surface light can be minimized. Such a propertyresults in construction of a compact, slim, and light LCD.

Although the illustrative embodiments have been described herein withreference to the accompanying drawings, it is to be understood that thepresent invention is not limited to those precise embodiments, and thatvarious other changes and modifications may be affected therein by oneof ordinary skill in the related art without departing from the scope orspirit of the invention. All such changes and modifications are intendedto be included within the scope of the invention as defined by theappended claims.

What is claimed:
 1. A light emitting diode comprising: a first lensincluding a bottom surface, a first surface extending from the bottomsurface, a second surface extending from the first surface, a thirdsurface extending from the second surface and a hollow portion; a secondlens; and a light emitting chip disposed under the second lens, whereinthe second surface has a convex shape that curves inward toward a centeraxis of the first lens and the third surface has a concave shape,wherein the second lens is disposed in the hollow portion and covers thelight emitting chip, and wherein a projection from above of the firstsurface, second surface, and third surface are each contained within thebottom surface.
 2. The light emitting diode of claim 1, wherein acurvature of the first surface is different from a curvature of thesecond surface.
 3. The light emitting diode of claim 2, wherein thesecond lens has a dome shape.
 4. The light emitting diode of claim 3,wherein the distance between a bottom surface of the second lens and thethird surface is shortest at the center of the bottom surface of thesecond lens.
 5. The light emitting diode of claim 4, wherein the hollowportion is formed from the bottom surface of the first lens.
 6. Thelight emitting diode of claim 3, wherein the hollow portion is formedfrom the bottom surface of the first lens.
 7. The light emitting diodeof claim 2, wherein the distance between a bottom surface of the secondlens and the third surface is shortest at the center of the bottomsurface of the second lens.
 8. The light emitting diode of claim 7,wherein the hollow portion is formed from the bottom surface of thefirst lens.
 9. The light emitting diode of claim 2, wherein the hollowportion is formed from the bottom surface of the first lens.
 10. Thelight emitting diode of claim 1, wherein the second lens has a domeshape.
 11. The light emitting diode of claim 10, wherein the distancebetween a bottom surface of the second lens and the third surface isshortest at the center of the bottom surface of the second lens.
 12. Thelight emitting diode of claim 11, wherein the hollow portion is formedfrom the bottom surface of the first lens.
 13. The light emitting diodeof claim 10, wherein the hollow portion is formed from the bottomsurface of the first lens.
 14. The light emitting diode of claim 1,wherein the distance between a bottom surface of the second lens and thethird surface is shortest at the center of the bottom surface of thesecond lens.
 15. The light emitting diode of claim 14, wherein thehollow portion is formed from the bottom surface of the first lens. 16.The light emitting diode of claim 1, wherein the hollow portion isformed from the bottom surface of the first lens.
 17. A light emittingdiode comprising: a first lens including a bottom surface, a firstsurface extending from the bottom surface, a second surface extendingfrom the first surface, a third surface extending from the secondsurface and a hollow portion; and a light emitting chip disposed in thehollow portion, wherein the second surface has a convex shape thatcurves inward toward a main axis of the first lens and the third surfacehas a concave shape and wherein a flux of light ray emitted from thelight emitting diode has a highest value in between 70 degree and 80degree of incident angle, the incident angle is measured from the mainaxis of the first lens.
 18. The light emitting diode of claim 17,further comprising a second lens that is disposed in the hollow portionand covers the light emitting chip.
 19. The light emitting diode ofclaim 17, wherein, n is a refraction index of the first lens, A1 is anobtuse angle formed between the main axis of the first lens and atangent line of a point of the third surface, A2 is an acute angleformed between a straight line linking a center of the bottom surface tothe corresponding point of the third surface and the main axis of thelens, and A1+A2<90+sin⁻¹(1/n).
 20. A light emitting diode comprising: afirst lens including a bottom surface, a first surface extending fromthe bottom surface, a second surface extending from the first surface, athird surface extending from the second surface and a hollow portion;and a light emitting chip disposed in the hollow portion, wherein thesecond surface has a convex shape that curves inward toward a main axisof the first lens and the third surface has a concave shape and wherein,n is a refraction index of the first lens, A1 is an obtuse angle formedbetween the main axis of the first lens and a tangent line of a point ofthe third surface, A2 is an acute angle formed between a straight linelinking a center of the bottom surface to the corresponding point of thethird surface and the main axis of the lens, and A1+A2<90+sin⁻¹(1/n).21. The light emitting diode of claim 20, further comprising a secondlens that is disposed in the hollow portion and covers the lightemitting chip.